Anders Behring Breivik's mother "sexualised" her four-year-old son and often told him she wished he were dead, according to child psychologist reports.

The reports also show that his mother became preoccupied with fears that he would assault someone.

"She saw him as an adult violent person, though he was only a small boy," said Aage Borchgrevink, author of 'A Norwegian Tragedy'.

The psychologist reports show that Wenche Behring already felt that her son was "aggressive, hyperactive and clingy" when she was breastfeeding him. By the time he was four, she "sexualised" him, hit him, and frequently told him that she wished he were dead.

"The mother and Anders sleep in the same bed at night with very close bodily contact," psychologists from Norway's centre for child and youth psychiatry (SSBU) reported in 1983.

The family's neighbours had become worried about her inappropriate sexual behaviour.

"During the police investigation, the neighbours also said they had been shocked by the mother's sexualised language," Mr Borchgrevink writes. "There was a lot of fighting in the apartment and they remembered sexual activity taking place while the children were in there."

The psychologists reported that she would frequently tell her son that she wished he would die. When she smacked him in an attempt to exert control, the four-year-old would taunt her that the blows did not hurt, smiling in a way she found "condescending, inappropriate and derisive".